1. Field of the Invention
The present invention relates to apparatus for inspecting piping. More particularly, the present invention relates to an instrument carriage for use with a pipe crawler to inspect the structural integrity of the interior surface of piping.
2. Discussion of Background
Numerous instrumentation exists for verifying the integrity of piping, including devices for examining their interior and exterior surfaces. Quite often, a scanning device such as an ultrasonic scanner can be used to inspect the exterior surface of piping that is readily accessible.
For piping that is not readily accessible, such as buried piping or piping carrying radioactive or other hazardous materials, devices that inspect the piping's interior surface are often the only means for verifying the integrity of the piping. Some inspection means are self-propelled pipe crawlers having the desired instrumentation mounted thereon. For example, see the pipe crawling devices described by Metal et al in U.S. Pat. No. 4,856,337, Cowell in U.S. Pat. No. 3,926,040 and Weber et al in U.S. Pat. No. 4,460,920.
Other inspection devices consist of carriages transported through the piping by pipe crawlers or other means. A suitable pipe crawler for the present invention and other instrument carriages is described in commonly-assigned U.S. Pat. No. 5,121,694, whose disclosure is incorporated herein by reference. Also, see commonly-assigned U.S. Pat. No. 5,018,451 for a description of another pipe crawler that could be used to move a pipe inspection carriage.
Inspection carriages are well known in the art. Some carriages carry a plurality of inspection equipment, such as ultrasonic probes, eddy current sensors, cameras and the like, but often have limited mobility within the piping once transported therein. Still other carriages carry only selected instruments but offer greater degrees of movement for using the transported equipment.
For example, Nottingham et al, in U.S. Pat. No. 4,864,862, disclose an ultrasonic inspection system featuring a carriage with two radial support assemblies that can move separately to tilt transducers mounted on the carriage.
In U.S. Pat. No. 5,189,915, Reinhart et al disclose an ultrasonic inspection method and apparatus having a carriage that includes a plurality of search units mounted on a housing located between two centering donuts. Each donut contains three dowels spaced 120.degree. apart, for centering the device within the pipe interior. The carriage is also capable of supplying couplant.
Gunkel, in U.S. Pat. No. 3,766,775, discloses a transducer assembly that is rotated within the interior of piping. The device is mounted on a rotable shaft, and the transducer mechanism is stabilized within the pipe by a portable stand. A motor extending from the portable stand controls the movement of the transducer assembly.
Despite the number of carriages that exist, it is desirable to have an instrument-carrying carriage for ultrasonic inspection of piping interior that has greater axial range, yet is still dimensioned to negotiate piping bends.